Most modern computers employ data storage systems including hard disk drives (HDDs)—that is systems in which an inflexible disk including magnetic material stores data which is written/read by a magnetic head which moves over the surface of the disk but does not come into physical contact with the disk. Hard disk drives provide high capability for storing information, and over the years, the data storage capacity of HDDs has been increased by several technological innovations, such as the use of GMR (Giant Magneto-Resistive) heads and fluid bearing type spindle motors. So far, however, the usage of HDDs has been restricted to storing information in computer systems, rather than in smaller items of consumer electronics. Recently, with increasing demand for portable consumer products, such as PDAs and cellular phones, there has been an increasing need for a small HDD, but it is difficult to produce small HDDs by applying conventional production methods such as precision machining and assembly techniques because there are difficulties in producing smaller parts and assembling them. For example, the spindle motor of an HDD basically consists of a stator and a rotor which carries magnetic disks. Both the stator and the rotor consist of several parts, such as a shaft, a magnet and coils.
In addition, the requirements for the mechanical performance of an HDD are highly demanding, because high reliability is required of a HDD system. Apart from high precision in the fabrication of the rotor and stator, precise mechanical control is required of other components too, such as the actuator which moves the head used for reading data from the magnetic disk.